2018 ASHS Annual Conference

Protective netting is becoming a widespread technique all around the world. Originally, netting was developed to protect high value perennial crops from hail damage. In some countries the hail risk is covered by insurance. Insurance can protect crop loss but there are other indirect damages that are very difficult to recover. In the case of perennial trees affected by a strong hail storm, not only the current crop can be lost but also the crop of the following year due to the damage of the flower buds. In addition, wounds can become a penetration point for disease like bacteria (Erwinia amylovora fire blight) or fungi. In Europe, netting was developed in the 1970s and there were different shapes of the protective structure. The utilization of netting is associated with the increase of planting density and the modification of the tree canopy related to the use of dwarfing rootstocks. The original structure was initially made of tall posts and a triangular structure to support the net on the top. The use of dwarfing rootstocks, like M9 for apple and Quince for pear, that reduced tree height allowed the structure to become more flat and less expensive by saving on the cost of posts and net. The increasing cost of HDP orchard establishment justify the use of protective netting. Additional advantages of netting are protection against bird, especially in cherry, insect and physiological stress. The Alt-carpo system developed in France in 2005 and validated in 2006 by Severac, is a physical barrier to reduce the damage of Codling moth by the net's mesh size. This system creates a completely closed net with only one gate to enter and can be applied for large areas or to single row (drop net). All these solutions to cover full orchards or a single row increases benefits for the growers to make production more sustainable. Nets modify physiological conditions of the tree because they induce microclimatic variation. Protective netting primarily modifies light quantity and quality by reducing light intensity by an approximately pre-determined percentage. Protective netting has also been reported to reduce wind speed and soil temperature with minimal impact on canopy temperature, relative humidity and with important effects on fruit quality.